To make the buckwheat: Preheat the oven to 400˚F. Spread out the buckwheat on a baking sheet. Toast in the oven until the buckwheat deepens in color and has a nutty aroma, about 8 minutes. Let cool, then use a mortar and pestle to crush the buckwheat into a texture resembling coarse sand.: As the toasted buckwheat warms on the baking sheet you will notice a deepening color and a fragrance that shifts from grainy to nutty, almost like toasted sunflower seeds. This aroma is your best visual cue that the toasting is working. When you break the cooled kernels with a mortar and pestle into coarse sand they should clatter softly and feel dry, not oily. The reason to crush them after toasting is to preserve that delicate crunch rather than releasing oils prematurely. A common mistake is leaving them in the oven too long, which turns the pleasant nuttiness into bitter char, so check at the eight minute mark and smell for that sweet toastiness.
To prep the salad ingredients: While the buckwheat is toasting, thinly slice the radish into half-moons and transfer to a small bowl of ice water until ready to use. Place the lettuce in a large serving bowl.: The crisp sound of thinly sliced radish hitting the bowl of ice water is a small reward, and the cold soak helps the slices snap and mellow their peppery edge. Meanwhile, when you move the loose lettuce into a large serving bowl it should look fluffy and airy, ready to cradle the dressing. Drain and dry the radish well so it does not water down the salad, because excess moisture can make the leaves limp. Avoid slicing the radish too thickly, which can overwhelm each bite and throw off the texture balance.
To make the dressing: Place the garlic in a blender or food processor and pulse it into small pieces. Add the remaining dressing ingredients and blend until smooth.: When you pulse the garlic and blend it with the herbs, yogurt , lemon juice , olive oil , and mustard , the mixture should smell bright and herbaceous, with the garlic softened into the background. The texture should be smooth and glossy, not grainy, indicating the oil has emulsified. This blending step is important because it distributes herb flavor evenly and tames raw garlic. A common pitfall is under blending, which leaves harsh garlic bits or unincorporated oil, so process until silky.
To assemble the salad: Drain and pat dry the radish slices. Add a handful to the bowl of lettuce along with 1/3 cup of the dressing. Reserve the remaining dressing for another use. Toss until everything is well coated. Top with the remaining radish and a hefty sprinkle of the crushed buckwheat and some black pepper.: As you toss the drained radish with a portion of the dressing and the bed of lettuce , listen for the gentle rustle of coated leaves and note how the dressing clings to surfaces rather than pooling. The initial toss should evenly coat the leaves so each forkful has balance, and reserving dressing allows you to adjust seasoning after tasting. A typical error is overdressing, which overwhelms the delicate greens and masks the crushed buckwheat , so start modestly and add more if needed.
To finish and serve: The final act of scattering the crushed, toasted buckwheat over the top adds an audible, delicate crunch when you cut through it with a fork, and a final crack of black pepper lifts the whole dish. Visually, the contrast between pale yogurt flecks, bright pink radish slices, and toasted brown bits makes the salad inviting. If the buckwheat feels soft instead of crisp, it likely sat too long with the dressing and lost its texture, so sprinkle it right before serving for maximum crunch.
